In recent years, use of mobile communications devices for voice telephone services, email or text messaging services and even multi-media services has become commonplace, among mobile professionals and throughout the more general consumer population. Mobile service provided through public cellular or PCS (personal communication service) type networks, particularly for voice telephone service, has become virtually ubiquitous across much of the world. In the USA, for example, competing public networks today provide mobile communications services covering most if not all of the geographic area of the country.
In addition to public networks, similar wireless technologies have provided relatively small scale networks for enterprise applications, typically offering wireless service analogous to private branch exchange (PBX) type service. Such a smaller scale private system includes several base stations, similar to but scaled down from those used in the public networks, in combination with a private circuit switch or more recently an Internet Protocol (IP) router or network, for providing communications between devices and with external networks. U.S. Pat. No. 6,970,719 to McConnell et al. and US application publication no. 2005/0059390 to Sayers et al. disclose examples of such private wireless cell phone networks. Although sometimes referred to as an “indoor cellular network” or “indoor system,” such enterprise systems need not be literally indoors and for example may offer coverage across an entire campus area. Alternatively, such an enterprise cellular communication system may be referred to as a “pico-cell” system, with the outdoor public cellular communication system covering a wider area being referred to as a “macro-cell” system.
As broadband IP connectivity to homes and offices has become more common, and the speeds of packet-switched communications equipment and the speed of processors have increased, a variety of applications have emerged that utilize IP packet transport as an alternative bearer for voice communications. Generally, such applications are referred to as voice-over-packet services, however, the common forms based on Internet Protocol (IP) are referred to as “Voice over IP” or “VoIP” services. Although originally developed for wireline network transport through the Internet and through wireline intranets, VoIP services are now migrating to the wireless domain. For example, pico cell systems, which use IP routing or frame switching for IP transport, utilize VoIP technology to support the voice services.
As an extension of these developments/deployments into the customer premises, particularly for residential or small business applications, equipment manufacturers have recently begun offering “femto” cell devices, e.g. for home installation. A “femto” cell system includes a small scale base transceiver system (BTS) for wireless communication with mobile stations, so as to operate compact base station. In recent examples, the BTS has VoIP capability and an IP interface, for example, for connection to a digital subscriber line (DSL) modem or to a cable modem. If it includes VoIP capability and an IP interface, the femto base station may be referred to as an “IP-BTS.” One femto cell unit in a home or small business would allow mobile station users in or around the premises to make and receive calls. If the femto cell is an IP-BTS type device the calls would use the existing broadband wireline service from the customer's Internet Service Provider (ISP).
It has been suggested that the deployment of femto cells will be particularly advantageous to a carrier as a way to improve mobile communication service of the carrier's macro network in customer premises locations where the macro network service is less than optimum. For example, if a mobile station user may have weak coverage at his or her residence, installation of a femto cell in the home effectively extends macro network coverage into the home in a manner that substantially improves the customer's experience using the carrier's network.
At present, plans therefore are for the carrier(s) to distribute (sell or lease) the femto cell equipment to their public macro network customers. The femto cell is intended to work with a regular mobile station. To the mobile station, the BTS of such a femto cell appears like a normal base station of the public network. Deployment of femto cells, particularly in large numbers of customer premises, requires coordination with networks of the applicable public carriers, which raises issues for such a carrier.
Femto cell products are deployed in customer locations as an underlay system. They are designed to have the same attributes as the macro network, to create a seamless network for customers. Since these femto cells for residential or small business deployments have limited resources for providing service, the carrier may offer the femto cell customers the ability or option to designate their devices as “private” access points for a predefined list of associated mobile stations. When so configured, all other mobile stations will be denied service under the coverage of these privatized femto BTS devices. However, based on RF conditions, any mobile station may lock-onto a private BTS of a femto cell, but the mobile station will not be aware that it can not obtain service through that BTS, because the femto BTS otherwise appears as a public device to the mobile station. Under such a circumstance, a mobile station that is not on the list of customer-approved stations for the private femto BTS may be locked onto that BTS, but because the mobile station is not associated with the femto cell for private access, the femto BTS will block service for calls to/from the network for that non-associated mobile station. Such conditions disrupt service for other regular customers of the mobile service provider when those mobile stations conduct an idle-handoff into these private BTS devices given their proximity and RF conditions. Therefore, a need exists for a technique to gracefully handle these mobile devices that are “foreign” to the private femto BTS, without blocking services to the foreign mobile stations, while maintaining the security and resource management of the privately designated femto BTS equipment.